Question

Problem 2: Consider an assembly of 3 major components: electromotor (EM), pump (PIP) and valve (V/V). The EM and pump come always together. Valve is separate EM P/P VV We buy the EM-Pump assembly from Germany, China, and USA. We run the German set and the others from USA and China 'as backup. The reliability given by the manufacturer from these countries are: Germany: 0.95 for each of the EM and the Pump USA: 0.90 for each of the EM and the Pump China: 0.85 for each of the EM and the Pump We buy 2 valves with the same reliability (0.95). One valve is the backup for the other valve. Draw the diagram and calculate the reliability of our system that has 8 parts (one method is enough).

Answer 1

Reliability of German set = 0.95*0.95 =0.9025

Reliability of US set =0.9x0.9=0.81

Reliability of China set =0.85*0.85 =0.7225

Reliability of a combination where German set is used as main set and other two as backup

= 1- [ (1-0.9025)*(1-0.81)*(1-0.7225)]

= 1- [ 0.0975*0.19*0.2775]

=1-0.00514 =0.99486

Reliability of system of valves = 1-(1-0.95)*(1-0.95) =0.9975

Resultant reliability = 0.99486*0.9975 =0.99237

Diagram

China EMAPP JEMAPP EMAPP -v German